Digital High-Resolution Torque Sensor and Signal Processing

Abstract

A contactless thin-layered torque sensor with fully digital signal processing circuit is proposed in this paper. The mechanical structure of the torque sensor is an orange-slice-alike flexible body. Two links with black/white stripes are aligned beforehand as no any torque applied to the shaft. The two links play the role of optical grating by resolution. As long as the orange-slice-alike flexible body, sandwiched by the aforesaid links, is subject to an external torque applied, a twisted angle is induced between the two thin photograting discs. Two sets of photodetector cooperate with the two discs with optical gratings to generate two pulse sequences. Therefore, a time delay between these two pulse sequences can be acquired as long as the shaft is twisted by a torque. A counter IC is employed to quantify this time delay in terms of the torque applied, and the time period in terms of rotational speed of shaft. One of the merits of the proposed torque sensor is that real-time measurement on torque applied becomes feasible even if the shaft, subject to external torque, is rotating at high speed. Other advantages of the fully digital signal processing circuit include: 1) no need to conduct analog/digital conversion and 2) free of noise, crosstalk and electromagnetic interference.